The present invention relates to a fuel injector for fuel injection systems of internal combustion engines.
European Patent 348 786 B1 describes a fuel injector for an internal combustion engine having a nozzle body which has a transverse wall with an inner side and an outer side, a fuel channel leading to the outside through the transverse wall, and an outer chamber which is situated on the outer side of the transverse wall and extends between the transverse wall and an outlet opening and is delimited by a cylindrical wall of the nozzle body, which cylindrical wall has a length such that the fuel channel is kept free of deposits. This fuel injector is intended for injection of fuel into an intake manifold for the internal combustion engine.
The disadvantage of this type of known fuel injector is that the geometry of the fuel-jets through the outer cylinder is greatly limited, and the fuel injector is only usable for direct fuel injection with limitations. Furthermore, it is disadvantageous that the volume and the installation space of the outer cylinder, which screens off the fuel channel, interfere in the combustion chamber at the end of the compression stroke. In addition, arcing through of the fuel mixture in the outer cylinder cannot be prevented and, despite the screening-off effect of the outer cylinder, temperature peaks and coking may occur.
Published German Patent Application 198 04 463 A1 describes a fuel injection system for a compressed-mixture, externally-fired internal combustion engine, which includes a fuel injector that injects fuel into a combustion chamber formed by a piston/cylinder construction, and which is provided with a spark plug protruding into the combustion chamber. The fuel injector is provided with at least one row of injection holes distributed over the circumference of the fuel injector. By forming a mixture cloud using at least one jet, jet-controlled combustion is implemented through controlled injection of fuel through the injection holes.
The disadvantage of the fuel injector described in the above-mentioned document is that coking of the injection openings is not prevented. Because the fuel injector injects directly into a combustion chamber, it is subject to higher thermal stresses. Furthermore, due to the plurality of injection openings, the diameter of the injection openings is made smaller in order to allow small fuel amounts to be injected. The relative surface area in the injection bores wetted by fuel is larger and coking occurs more easily, which in turn results in impaired fuel jet and mixture formation.
The fuel injector according to the present invention provides the advantage over the conventional injectors in that coking deposits may be mechanically removed even in the case of very small injection openings, which may be oriented in any desired manner. Vibrations over the space of the injection opening are induced in the vibration element present in the flowing fuel in the injection opening by flow turbulence. The vibration element is in full or partial contact with the walls of the injection opening and is detached therefrom again. Thus, all wall areas of the injection opening are reached with a statistical distribution, and coking is mechanically knocked off and entrained by the flowing fuel. The vibration element is made of an elastic material and is mainly subject to tensile stress. Therefore, the vibration element may have a very small material thickness which only slightly affects the cross section of the injection opening and thus the shape of the jet.
The vibration element may be a metal thread, which is attached in a recess of the valve seat body on the inlet side of the injection opening by spot welding. This exemplary embodiment allows a heat-resistant, high tensile strength vibration element to be implemented in a cost-effective manner.